var CONTENT_TYPE = {
    '.avi': 'video/x-msvideo',
    '.bmp': 'image/bmp',
    '.doc': 'application/msword',
    '.docx': 'application/vnd.openxmlformats-officedocument.wordprocessingml.document',
    '.flv': 'video/x-flv',
    '.gif': 'image/gif',
    '.html': 'text/html',
    '.jpe': 'image/jpeg',
    '.jpeg': 'image/jpeg',
    '.jpg': 'image/jpeg',
    '.ico': 'image/x-icon',
    '.mkv': 'video/x-matroska',
    '.mov': 'video/quicktime',
    '.mp3': 'audio/mpeg',
    '.mp4': 'video/mp4',
    '.png': 'image/png',
    '.ppt': 'application/vnd.ms-powerpoint',
    '.psd': 'image/vnd.adobe.photoshop',
    '.xls': 'application/vnd.ms-excel',
    '.xlsx': 'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet',
    '.xsl': 'application/xml',
    '.zip': 'application/zip',
    '.rar': 'application/octet-stream',
    '.dbf': 'application/x-dbf',
    '.pdf': 'application/pdf'
};